This invention relates to a vessel for carrying slurry such as a mixture of pulverized iron ores and water, and more particularly, to an apparatus for automatically carrying out vacuum dehydration of slurry loaded within a hold of the vessel.
Generally, in a slurry carrying vessel, during several days soon after a departure with slurry loaded, the slurry in which compacting proceeds may be fluidified due to movement such as great rolling or vibration of a hull tending to apply an anomalous force to walls of a hold, and if no fluidity is present, compacting of the layer of slurry may often be accelerated, thus requiring excessive labor at the time of unloading.
Heretofore, in order to avoid these phenomena, it has been proposed to forcibly dehydrate the layer of slurry by means of a vacuum pump. However, this procedure involves problems such that if the dehydration is merely continued by means of the vacuum pump, there is a tendency to suck air present in the upper portion within the hold through cracks formed in the layer of locally compacted and solidified pulverized iron ores, and as a result, efficient dehydration cannot always be accomplished as a whole.
The present invention overcomes the disadvantages as noted above, and has it as an object to provide an apparatus wherein highly efficient vacuum dehydration may be automatically accomplished while controlling compacting of every portion of slurry loaded in a slurry carrying vessel.
One feature of the present invention is to provide an automatic vacuum dehydrating apparatus in a slurry carrying vessel which includes a hold for loading slurry therein provided with a plurality of dehydrating ports at its bottom, comprising a dehydrating pipe branched at one end and connected to said respective dehydrating ports through respective closure valves individually provided in the respective pipe branches, a vacuum tank adapted to be evacuated and connected to the other ends of said dehydrating pipes, pressure detector-controller means for detecting a pressure in the vicinity of each said dehydrating port and for controlling said closure valve in response to the detected pressure value, in such manner that when said detected pressure exceeds a predetermined value the closure valve in the corresponding dehydrating pipe branch may be closed.
Another feature of the present invention is to provide the above-featured automatic vacuum dehydrating apparatus in a slurry carrying vessel, in which said pressure detector-controller means is also adapted to control said closure valve in response to the detected pressure value, in such manner that when said detected pressure is further raised up to a preset upper limit value, the same closure valve in the corresponding dehydrating pipe branch may be opened again.
Still another feature of the present invention is to provide the above-featured automatic vacuum dehydrating apparatus in a slurry carrying vessel, in which said vacuum tank is in turn connected to a vacuum pump and a drainage pump, and is provided with a water level detector-controller means for detecting a level of water accumulated in said vacuum tank and for selectively controlling said drainage pump and said vacuum pump in response to the detected water level in said vacuum tank, in such manner that when the detected water level in said vacuum tank exceeds a first predetermined level said drainage pump is actuated and said vacuum pump is stopped to drain the accumulated water, whereas when the detected water level in said vacuum tank is lowered under a second predetermined level said vacuum pump is actuated and said drainage pump is stopped to evacuate said vacuum tank.
Yet another feature of the present invention is to provide the above-featured automatic vacuum dehydrating apparatus in a slurry carrying vessel, in which said vacuum tank is connected to a vacuum pump via a first additional closure valve at its upper wall portion, to a drainage pump via a second additional closure valve at its lower wall portion, to the atmosphere via a third additional closure valve at its upper wall portion, and to said dehydrating pipe via a fourth additional closure valve, and in which said water level detector-controller means responds to the detected water level in said vacuum tank for selectively controlling said drainage pump, said vacuum pump and said first, second, third and fourth additional closure valves, in such manner that when the detected water level in said vacuum tank exceeds a first predetermined level, said drainage pump is actuated and said vacuum pump is stopped, while closing said first and fourth additional closure valves and opening said second and third additional closure valves, whereas when the detected water level in said vacuum tank is lowered under a second predetermined level, said vacuum pump is actuated and said drainage pump is stopped, while opening said first and fourth additional valves and closing said second and third additional closure valves.
In accordance with the automatic vacuum dehydrating apparatus of the present invention, the closure valve in each dehydrating pipe may be continuously controlled in a proper manner while detecting suction pressure by means of a pressure detector-controller unit, with respect to each of the dehydrating ports formed at the bottom of the hold, so that the stoppage of vacuum hydration caused by suction of air may be eliminated, and in addition, when the water accumulated within the vacuum tank by the dehydrating operation exceeds a predetermined level, a water level detector-controller unit which detects the water level, achieves automatic control so as to stop the vacuum pump and to actuate the drainage pump. In this manner, the vacuum dehydration of the slurry as a whole, may be automatically and efficiently accomplished.
These and other objects, features and advantages of the present invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawing, in which the single figure is a schematic diagram illustrating an arrangement and connections of principal component parts of an automatic vacuum dehydrating apparatus in a slurry carrying vessel according to one preferred embodiment of the present invention.